Stress-resistant component for use with quantum dots

ABSTRACT

A glass tube including quantum dots in a polymerized matrix is described. An optical component and other products including such glass tube, a composition including quantum dots, and methods are also disclosed.

CLAIM OF PRIORITY

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/562,468, filed on Nov. 22, 2011, which is hereby incorporatedherein by reference in its entirety for all purposes.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the generation of light usingsemiconductor nanocrystals, also referred to as quantum dots, includedwithin a capillary structure and their use in structures for lightingand display applications.

BACKGROUND OF THE INVENTION

Liquid crystal displays (LCDs) are the dominant flat panel displaytechnology in today's market. Conventional LCD systems include a networkof optical components in front of a light source (e.g., fluorescentlamps, light emitting diodes (LEDs), etc.) commonly referred to as abacklight unit (BLU). Conventional backlight units include a lightsource coupled to a light guide through which the light travelseventually to a display panel. LED backlights employed in conventionalsystems include a set of optical films placed on top of an LED source, aslight distance away from the source. Among other things, the selectionof a proper distance between the LED source and the associated opticalfilms ensures that the light entering the display panel is properlyoptimized.

The quality of an LCD is often measured by a color gamut diagram. Thecolor gamut refers to the total space of colors that may be representedby a display. Generally, the color gamut is shown by diagrams such asthe International Commission on Illumination (CIE) 1931 XY colordiagram. In this diagram, the gamut of available colors is representedby chromaticity on the x axis and brightness or luminance on the y axis.The gamut of all visible colors on a 2-D CIE plot is generallyrepresented by a tongue shaped area in the center of the diagram.

Increasing the color gamut of a display device increases color qualityand also leads to a higher perceived brightness. This effect is known asthe Helmholtz-Kohlrauch (H-K) effect, which is defined as “Change inbrightness of a perceived color produced by increasing the purity of acolor stimulus while keeping its luminance constant within the range ofphotopic vision.” (See CIE Publication No. 17.4, International LightingVocabulary, Central Bureau of CIE, Vienna, 1988, sec. 845-02-34, p. 50.)This effect is dependent on ambient lighting conditions (i.e., theeffect is enhanced under lower ambient lighting conditions and isdiminished under higher ambient lighting conditions).

Two different LED light sources have been utilized in LCDs: (1) thecombination of red, green and blue (RGB) LEDs and (2) white LEDs.Compared to the use of white LEDs, the use of RGB LEDs allows for abetter color gamut but also adds significant complexity inimplementation. The reduced complexity and, therefore reduced cost, ofwhite LED backlights has caused these structures to be theimplementation of choice in commercial LCD displays. Thus, someconventional displays have only a 70% color gamut (relative to the 1953NTSC standard). In addition, some conventional LED sources requirenumerous color filters in the optical stack which increases powerconsumption.

LEDs commonly use phosphors to generate white light. The quality, colorand directionality of light produced by LEDs are often poor. Opticalcomponents including quantum dots can be combined with an LED to producelight of certain wavelengths.

Accordingly, one object of the present invention is to increaseperformance of solid state lighting devices that utilize opticalcomponents including quantum dots.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to an optical materialincluding quantum dots (including, e.g., semiconductor nanocrystals) togenerate light. According to one aspect, a combination of certainquantum dots of the present invention, such as quantum dots that emitgreen light wavelengths and quantum dots that emit red lightwavelengths, that are stimulated by an LED emitting blue lightwavelengths results in the generation of trichromatic white light.According to one aspect, the quantum dots are contained within anoptical component such as a tube which receives light from an LED. Lightgenerated by the quantum dots is delivered via a light guide for usewith display units. According to certain aspects, light generated byquantum dots, such as trichromatic white light, is used in combinationwith a liquid crystal display (LCD) unit or other optical display unit,such as a display back light unit. One implementation of the presentinvention is a combination of the quantum dots within a tube, an LEDblue light source and a light guide for use as a backlight unit whichcan be further used, for example, with an LCD unit.

Optical components that include quantum dots according to the presentinvention include tubes of various configurations, such as length,width, wall thickness, and cross-sectional configuration. The term“tube” as used in the present disclosure includes a capillary, and theterm “tube” and “capillary” are used interchangeably. Tubes of thepresent invention are generally considered light transmissive such thatlight can pass through the wall of the tube and contact the quantum dotscontained therein thereby causing the quantum dots to emit light. Tubesof the present invention are configured to avoid, resist or inhibitcracking due to stresses placed on the tube from polymerizing a matrixtherein or heating the tube with the polymerized matrix therein. In thisaspect, the tubes of the present invention are glass tubes for use withquantum dots. Such tubes can have a stress-resistant configuration andexhibit advantageous stress-resistant properties. The tube containingthe quantum dots is also referred to herein as an optical component. Anoptical component can be included as part of a display device.

According to one aspect, the tube of the present disclose is made from atransparent material and has a hollow interior. Quantum dots residewithin the tube and may be contained within a polymerized matrixmaterial which is light transmissive. A polymerizable compositionincluding quantum dots and at least monomers can be introduced into thetube and then polymerized within the tube using light, for example. Thetube may be sealed at one or both ends. The tube has sufficienttolerance or ductility to avoid, resist or inhibit cracking during thecuring of the monomers into a polymerized matrix material within thetube. The tube also has sufficient tolerance or ductility to avoid,resist or inhibit cracking during thermal treatment of the tube with thepolymerized quantum dot matrix therein. According to certain aspects,the components for making a polymerized quantum dot matrix includepolymerizable materials exhibiting ductility when polymerized. Accordingto certain aspects, the components for making a polymerized quantum dotmatrix include materials which resist yellowing, browning ordiscoloration when subject to light. According to one aspect, thecombination of the tube of the present invention and the ductilepolymerized matrix result in a stress resistant or crack resistantoptic.

Embodiments of the present invention are directed to the mixtures orcombinations or ratios of quantum dots that are used to achieve certaindesired radiation output. Such quantum dots can emit red and green lightof certain wavelength when exposed to a suitable stimulus. Still furtherembodiments are directed to various formulations including quantum dotswhich are used in various light emitting applications. Formulationsincluding quantum dots may also be referred to herein as “quantum dotformulations” or “optical materials”. For example, quantum dotformulations can take the form of flowable, polymerizable fluids,commonly known as quantum dot inks, that are introduced into the tubeand then polymerized to form a quantum dot matrix. The tube is then usedin combination with a light guide, for example.

Such formulations include quantum dots and a polymerizable compositionsuch as a monomer or an oligomer or a polymer capable of furtherpolymerizing. Additional components include at least one or more of acrosslinking agent, a scattering agent, a rheology modifier, a filler, aphotoinitiator and other components useful in producing a polymerizablematrix containing quantum dots. Polymerizable compositions of thepresent invention include those that avoid yellowing when in the form ofa polymerized matrix containing quantum dots. Yellowing leads to alowering of optical performance by absorbing light emitted by thequantum dots and light emitted by the LED which can lead to a shift inthe color point.

Embodiments of the present invention are still further directed tovarious backlight unit designs including the quantum dot-containingtubes, LEDs, and light guides for the efficient transfer of thegenerated light to and through the light guide for use in liquid crystaldisplays. According to certain aspects, methods and devices are providedfor the illumination and stimulation of quantum dots within tubes andthe efficient coupling or directing of resultant radiation to andthrough a light guide.

Additional aspects include providing a tube design, having one or bothends sealed, which withstands stresses relating to polymerization of apolymerizable quantum dot formulation therein or stresses relating toheating the tube containing the polymerized quantum dot matrix therein.Such tube design advantageously avoids, resists or inhibits crackingfrom such stresses which can allow oxygen into the tube. Oxygen and/orwater may degrade quantum dots during periods of high light fluxexposure. Accordingly, an optical component including a glass tubehaving advantageous or improved stress-resistant properties can improvethe performance of a polymerized quantum dot-containing matrix disposedtherein.

Embodiments are further provided for a backlight unit including quantumdots within a stress-resistant tube such as a glass tube describedherein having each end sealed and positioned within the backlight unit,and component to, an LED. Preferably, a polymer matrix that avoids,resists or inhibits yellowing is utilized. Such a polymerized quantumdot matrix may have a component that increases ductility of the matrixwhich avoids, resists or inhibits cracking of the matrix due toshrinkage. One exemplary material is lauryl methacrylate. Such an LED ofthe present invention utilizes quantum dots to increase color gamut andgenerate higher perceived brightness.

Embodiments are further provided for a display including an opticalcomponent taught herein.

Embodiments are still further provided for a device (e.g., but notlimited to, a light-emitting device) including an optical componenttaught herein.

Each of the original claims set forth at the end of the presentapplication are hereby incorporated into this Summary section byreference in its entirety.

The foregoing, and other aspects and embodiments described herein allconstitute embodiments of the present invention.

It should be appreciated by those persons having ordinary skill in theart(s) to which the present invention relates that any of the featuresdescribed herein in respect of any particular aspect and/or embodimentof the present invention can be combined with one or more of any of theother features of any other aspects and/or embodiments of the presentinvention described herein, with modifications as appropriate to ensurecompatibility of the combinations. Such combinations are considered tobe part of the present invention contemplated by this disclosure.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention as claimed. Other embodimentswill be apparent to those skilled in the art from consideration of thespecification and practice of the invention disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIGS. 1A, 1B and 1C are drawings of a tube of the present invention.FIG. 1A is a face view of a tube of the present invention. FIG. 1B is asectional view along line A-A of FIG. 1A. FIG. 1C is a perspective viewof a tube of the present invention.

FIG. 2 is a flow chart describing a capillary fill procedure,

FIG. 3 depicts a photomicrograph of an example of a type of cracktypical of a prior art capillary.

FIG. 4 shows the normalized spectra of quantum dot (QD) ink in acapillary with cracks measured at time t=0 and t=87 hours.

FIG. 5 shows the normalized spectra of QD ink in an example of anembodiment of a capillary in accordance with the invention, withoutcracks, measured at time t=0 and t=87 hours.

FIG. 6 depicts a cross-section of a drawing of an example of anembodiment of a tube in accordance with the present invention.

FIG. 7 shows a schematic cross-sectional side view drawing depicting anexample of an embodiment of a back light unit in accordance with theinvention.

FIG. 8 schematically shows an example of an embodiment of a sealed glasstube containing matrix including quantum dots.

FIG. 9 schematically shows an exploded view of an example of anembodiment of a back light unit in accordance with the invention with adisplay unit.

The attached figures are simplified representations presented forpurposes of illustration only; the actual structures may differ innumerous respects, including, e.g., relative scale, etc.

For a better understanding to the present invention, together with otheradvantages and capabilities thereof, reference is made to the followingdisclosure and appended claims in connection with the above-describeddrawings.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention are directed to the use of astress-resistant tube such as a glass tube described herein thatincludes semiconductor nanocrystals, known as quantum dots, incombination with a stimulating light to produce light of one or morewavelengths including, e.g., trichromatic white light which can be usedin various lighting applications such as back light units for liquidcrystal displays. The glass tube is preferably light transmissive. Theglass tube described herein in combination with the quantum dots is alsoreferred to herein as an optical component.

According to certain aspects of the present invention, a vessel in theshape of a tube is provided which includes quantum dots. The tube ishollow and can be fashioned from various light transmissive materialsincluding glass.

According to one aspect, the tube has a stress-resistant orstress-tolerant configuration and exhibits stress-resistant orstress-tolerant properties when subjected to stresses from polymerizinga formulation therein or heating the tube with the polymerizedformulation therein. According to this aspect, a glass tube with suchstress-resistant or stress tolerant properties avoids, resists orinhibits cracking due to stresses during manufacture of an opticalcomponent including the glass tube, manufacture and/or use in a displaydevice, and during cycling of the display device. According to anadditional aspect, a glass tube with such stress-resistant or stresstolerant properties having a polymer matrix therein that includes amaterial that provides ductility avoids, resists or inhibits crackingdue to stresses during manufacture of an optical component including theglass tube, manufacture and/or use in a display device, and duringcycling of the display device. The tube has dimensions suitable forapplication within a display device. The glass tube may includeborosilicates. The glass tube may include soda lime. The glass tube mayinclude borosilicates and soda lime. The glass tube may be made fromother materials besides borosilicates or soda lime or may be made frommaterials in addition to borosilicates or soda lime. According to oneaspect, borosilicates are preferred materials for glass tubes of thepresent invention.

A tube within the scope of the present invention has a length of betweenabout 500 mm and about 1500 mm or between about 500 mm and 1200 mm andusually has a length comparable to a light guide within a displaydevice. A tube within the scope of the present invention has a wallthickness sufficient to withstand stresses due to the polymerization ofthe quantum dot matrix and heating of the tube and matrix combination.Suitable wall thicknesses include a thickness between about 250 micronsand about 700 microns, about 275 microns and about 650 microns, about300 microns and about 500 microns, about 325 microns and about 475microns, about 350 microns and about 450 microns, and about 350 micronsand about 650 microns and any value or range in between whetheroverlapping or not. Other thicknesses may be used based on the intendedend-use application.

According to certain embodiments, the tube has a cross-sectional wallconfiguration which produces stress-resistant or stress tolerantproperties. Configurations may include a circle, a rounded square, anoval, a racetrack configuration having parallel sides with full radiusends, and the like. According to certain aspects, the cross-sectionalconfiguration has a wall to wall outer major dimension between about 0.5mm and about 4.0 mm and a wall to wall inner minor dimension betweenabout 0.15 mm and about 3.3 mm.

FIGS. 1A, 1B and 1C depict an example of a tube in accordance with thepresent invention. FIG. 1A shows a face view of an example of a tube ofin accordance with the present invention. FIG. 1B depicts in schematicform a sectional view along line A-A of FIG. 1A, showing a tube having across-sectional wall design in the configuration of a racetrack.According to this aspect, the wall of the tube includes a first fullsemicircle or radius end and a second full semicircle or radius end. Thefirst full radius end and the second full radius end are connected byfirst and second substantially parallel walls. An exemplary tube havinga cross-sectional configuration of a racetrack is characterized as beingstress-resistant or stress-tolerant to the stresses or load on the tubedue to polymerization and curing of a polymerizable quantum dotformulation within the tube and additional stresses from heating thetube with the polymerized quantum dot matrix therein. Such an exemplarytube is referred to herein as a stress-resistant tube or stress-toleranttube. FIG. 1C shows a perspective view of an example of a tube inaccordance with the present invention.

According to one aspect, the walls are straight or flat and provide aconsistent or uniform path length through the tube and accordinglythrough the quantum dot matrix therein through which photons from an LEDmay pass. The substantially parallel and straight walls alsoadvantageously provide a flat face to couple the tube to a correspondingflat end of a light guide plate of a back light unit. According to oneaspect, the tube with the race track configuration has a cross-sectionaldiameter of between about 0.5 mm and about 5.0 mm in the elongatedirection (major dimension) and between about 0.15 mm and about 3.3 mmin the width direction (minor dimension). One example of a suitablecross sectional diameter is about 4 mm in the elongate direction byabout 1 mm in the width direction. According to one aspect, the fullradius ends advantageously bear higher loads than square cornered tubes.

FIG. 7 provides a schematic cross-sectional side view of an example ofan embodiment of a backlight unit in accordance with the invention,including a sealed glass tube described herein containing a matrixincluding quantum dots, light source(s) adjacent the sealed glass tubecontaining the matrix including quantum dots, and a light guide adjacentthe sealed glass tube. FIG. 9 schematically shows an exploded view of anexample of an embodiment of the invention including a sealed glass tubedescribed herein containing a matrix including quantum dots, lightsource(s) adjacent the sealed glass tube containing the matrix includingquantum dots, and a light guide adjacent the sealed glass tube incombination with a display unit.

As can be seen in FIG. 1B, the tube has a uniform wall thickness. Such awall thickness can be within the range of between about 60 and about 700microns. However, it is to be understood that the wall thickness may beuniform or nonuniform, i.e. of varying thickness. For example, the fullradius ends of the tube may be thicker than the straight wall portionsso as to provide greater stability. For example and with reference tothe cross-section of the tube, the full radius ends of the tube may bethinner than the straight wall portions. For purposes of this aspect,the wall thicknesses are measured as the distance between the outerfaces and the inner faces of the walls of the tube. The straight wallportions may be considered to have a uniform thickness or substantiallyuniform thickness along the length of the straight wall to a point wherethe straight wall terminates and a full radius end begins. The fullradius end may be considered to have a uniform thickness orsubstantially uniform thickness along the length of the full radius endto a point where the full radius end terminates and the straight wallportion begins. According to this aspect, the full radius end has athickness along its length which is smaller than the thickness along thelength of the straight wall portion. According to this aspect, the fullradius end has an average thickness along its length which is smallerthan the average thickness along the length of the straight wallportion. Such an exemplary tube where the thickness of the full radiusends is smaller than the thickness of the straight wall portion exhibitsless blue light leakage. Such an exemplary tube where the thickness ofthe full radius ends is smaller than the thickness of the straight wallportion exhibits enhanced color conversion. One exemplary wall thicknessis between about 310 microns and about 390 microns, such as about 315microns or about 380 microns. Such a wall thickness advantageouslyinhibits breakage of the tube during processing. As shown in FIG. 1B,the walls define an interior volume into which quantum dots are to beprovided in the form of a matrix. The interior volume is dependent uponthe dimensions of the stress-resistant tube. However, suitable volumesinclude between about 0.0015 ml and about 2.0 ml. In addition,stress-resistant tubes of the present invention have a ratio of thecross-sectional area of the matrix to the cross-sectional area of thewall of less than or equal to about 0.35. An exemplary ratiocharacteristic of a stress-resistant tube is about 0.35.

In addition to having full radius ends, capillaries of the presentinvention preferably have a predetermined ratio of glass wall thicknessto the volume of internal matrix. Control of such ratio can allow thecapillary to bear stress loads set up by both the shrinkage of thematrix monomers upon polymerization as well as the differentialexpansion and contraction of the polymer/glass system on thermalcycling. For example, for a capillary containing a cross-linkedLMA/EGDMA matrix system (e.g., described elsewhere herein), a matrixcross sectional area to glass cross sectional area ratio below 0.35 canbe preferred, although ratios as high as 0.7 can also be beneficial forcapillaries prepared from direct drawn glass. FIG. 6 depicts across-section of a drawing of an example of an embodiment of a tube inaccordance with the present invention showing dimensions related to thisratio.

According to one aspect, the length of the tube is selected based on thelength of the side of the light guide plate of the backlight unit alongwhich it is positioned. Such lengths include between about 50 mm andabout 1500 mm with the optically active area spanning substantially theentire length of the tube. An exemplary length is about 1100 mm or about1200 mm. It is to be understood that the length of the tube can beshorter than, equal to, or longer than the length of the light guideplate.

According to one aspect, one or both ends of the glass tube may besealed. The seal can be of any size or length. One exemplary dimensionis that the distance from the end of the capillary to the beginning ofthe optically active area is between about 2 mm to about 8 mm, withabout 3 mm or 5 mm being exemplary. Sealing methods and materials areknown to those of skill in the art and include glass seal, epoxy,silicone, acrylic, light or heat curable polymers and metal. Acommercially available sealing material is CERASOLZER available from MBRElectronics GmbH (Switzerland). Suitable metals or metal solders usefulas sealing materials to provide a hermetic seal and good glass adhesioninclude indium, indium tin, and indium tin and bismuth alloys, as wellas eutetics of tin and bismuth. One exemplary solder includes indium#316 alloy commercially available from McMaster-Carr. Sealing usingsolders may be accomplished using conventional soldering irons orultrasonic soldering baths known to those of skill in the art.Ultrasonic methods provide fluxless sealing using indium solder inparticular. Seals include caps of the sealing materials havingdimensions suitable to fit over and be secured to an end of the tube.According to one embodiment, one end of the tube is sealed with glassand the other end is sealed with epoxy. According to one aspect, theglass tube with a quantum dot matrix therein is hermetically sealed.Examples of sealing techniques include but are not limited to, (1)contacting an open end of a tube with an epoxy, (2) drawing the epoxyinto the open end due to shrinkage action of a curing resin, or (3)covering the open end with a glass adhering metal such as a glassadhering solder or other glass adhering material, and (4) melting theopen end by heating the glass above the melting point of the glass andpinching the walls together to close the opening to form a molten glasshermetic seal.

In certain embodiments, for example, a tube is filled with a liquidquantum dot formulation and UV cured in a nitrogen atmosphere. Accordingto one aspect, a stress-resistant tube, such as a borosilicate glasstube having a configuration described herein, is filled under oxygenfree conditions with the quantum dot formulation of Example III. Glasscapillaries are maintained under conditions of suitable time, pressureand temperature sufficient to dry the glass capillaries. A quantum dotink formulation of Example III is maintained in a quantum dot ink vesselunder nitrogen. Dried capillaries with one end open are placed into avacuum fill vessel with an open end down into quantum dot ink. Thequantum dot ink vessel is connected to the vacuum fill vessel via tubingand valves such that ink is able to flow from the quantum dot ink vesselto the vacuum fill vessel by applying pressure differentials. Thepressure within the vacuum fill vessel is reduced to less than 200 mtorrand then repressurized with nitrogen. Quantum dot ink is admitted intothe vacuum fill vessel by pressurization of the quantum dot ink vesseland the capillaries are allowed to fill under oxygen free conditions.Alternatively, the vacuum fill vessel can be evacuated thereby drawingthe fluid up into the capillaries. After the capillaries are filled, thesystem is bled to atmospheric pressure. The exterior of the capillariesare then cleaned using toluene.

According to an additional embodiment with reference to FIG. 2, acapillary with one end sealed is connected to a filling or manifold headcapable of docking with the capillary and switching between vacuum andink fill. The capillary is evacuated by a vacuum having a vacuumcapability of less than 200 mTorr. Quantum dot ink under nitrogenpressure is then filled into the capillary. The lines and filling headare flushed with nitrogen. The capillary is held under an atmosphere ofnitrogen or vacuum and the end sealed, such as by melting the capillaryend and sealing, for example by a capillary sealing system. The ink maythen be cured in the capillary using UV light in a UV curing apparatusfor curing quantum dot ink.

In certain embodiments, for example, the ink can be cured with an H or Dbulb emitting 900-1000 mjoules/cm² with a total dosage over about 1 toabout 5 minutes. Alternatively, curing can be accomplished using a Dymax500EC UV Curing Flood system equipped with a mercury UVB bulb. In suchcase, a lamp intensity (measured as 33 mW/cm² at a distance of about 7″from the lamp housing) can be effective, with the capillary being curedfor 10-15 seconds on each side while being kept at a distance of 7inches from the lamp housing. After curing, the edges of the capillarycan be sealed.

In certain embodiments relating to a temporary seal, sealing cancomprise using an optical adhesive or silicone to seal one or both endsor edges of the capillary. For example, a drop of optical adhesive canbe placed on each edge of the capillary and cured. An example of anoptical adhesive includes, but is not limited to, NOA-68T obtainablefrom Norland Optics. For example, a drop of such adhesive can be placedon each edge of the capillary and cured (e.g., for 20 seconds with aRolence Enterprise Model Q-Lux-UV lamp).

In certain embodiments, sealing can comprise using glass to seal one orboth ends or edges of the capillary. This can be done by brieflybringing a capillary filled with cured quantum dot ink into briefcontact with an oxygen/Mapp gas flame until the glass flows and sealsthe end. Oxygen-hydrogen flames may be used as well as any other mixedgas flame. The heat may also be supplied by laser eliminating the needfor an open flame. In certain embodiments, both ends of a capillaryfilled with uncured quantum dot ink can be sealed, allowing the ink tothen be photocured in the sealed capillary.

In certain embodiments, the capillary is hermetically sealed, i.e.,impervious to gases and moisture.

In certain embodiments, the capillary is pseudo-hermetically sealed,i.e., at least partially impervious to gases and moisture.

Other suitable techniques can be used for sealing the ends or edges ofthe capillary.

FIG. 8 schematically shows an example of an embodiment of a glass tubedescribed herein containing matrix including quantum dots and sealed atboth ends.

In certain aspects and embodiments of the inventions taught herein, thestress-resistant tube including the cured quantum dot formulation(optical material) may optionally be exposed to light flux for a periodof time sufficient to increase the photoluminescent efficiency of theoptical material.

In certain embodiments, the optical material is exposed to light andheat for a period of time sufficient to increase the photoluminescentefficiency of the optical material.

In preferred certain embodiments, the exposure to light or light andheat is continued for a period of time until the photoluminescentefficiency reaches a substantially constant value.

In one embodiment, for example, after the optic is filled with quantumdot containing ink, cured, and sealed (regardless of the order in whichthe curing and sealing steps are conducted), the optic is exposed, to25-35 mW/cm² light flux with a wavelength in a range from about 365 nmto about 470 nm, while at a temperature in a range from about 25° C. toabout 80° C., for a period of time sufficient to increase thephotoluminescent efficiency of the ink. In one embodiment, for example,the light has a wavelength of about 450 nm, the light flux is 30 mW/cm²,the temperature 80° C., and the exposure time is 3 hours. Alternatively,the quantum dot containing ink can be cured within the tube beforesealing one or both ends of the tube.

According to one aspect of the present invention, a polymerizablecomposition including quantum dots is provided. Quantum dots may bepresent in the polymerizable composition in an amount from about 0.05%w/w to about 5.0% w/w. According to one aspect, the polymerizablecomposition is photopolymerizable. The polymerizable composition is inthe form of a fluid which can be placed within the tube and then one orboth ends sealed with the tube being hermetically sealed to avoid oxygenbeing within the tube. The polymerizable composition is then subjectedto light of sufficient intensity and for a period of time sufficient topolymerize the polymerizable composition, and in one aspect, in theabsence of oxygen. The period of time can range between about 10 secondsto about 6 minutes or between about 1 minute to about 6 minutes.According to one embodiment, the period of time is sufficiently short toavoid agglomeration of the quantum dots prior to formation of apolymerized matrix. Agglomeration can result in FRET and subsequent lossof photoluminescent performance.

The polymerizable composition includes quantum dots in combination withone or more of a polymerizable composition. According to one aspect, thepolymerizable composition avoids, resists or inhibits yellowing when inthe form of a matrix, such as a polymerized matrix. A matrix in whichquantum dots are dispersed may be referred to as a host material. Hostmaterials include polymeric and non-polymeric materials that are atleast partially transparent, and preferably fully transparent, topreselected wavelengths of light.

According to an additional aspect, the polymerizable composition isselected so as to provide sufficient ductility to the polymerizedmatrix. Ductility is advantageous in relieving the stresses on the tubethat occur during polymer shrinkage when the polymer matrix is cured.Suitable polymerizable compositions act as solvents for the quantum dotsand so combinations of polymerizable compositions can be selected basedon solvent properties for various quantum dots.

Polymerizable compositions include monomers and oligomers and polymersand mixtures thereof. Exemplary monomers include lauryl methacrylate,norbornyl methacrylate, Ebecyl 150 (Cytec), CD590 (Cytec) and the like.Polymerizable materials can be present in the polymerizable formulationin an amount greater than 50 weight percent. Examples include amounts ina range greater than 50 to about 99.5 weight percent, greater than 50 toabout 98 weight percent, greater than 50 to about 95 weight percent,from about 80 to about 99.5 weight percent, from about 90 to about 99.95weight percent, from about 95 to about 99.95 weight percent. Otheramounts outside these examples may also be determined to be useful ordesirable.

Exemplary polymerizable compositions further include one or more of acrosslinking agent, a scattering agent, a rheology modifier, a filler,and a photoinitiator.

Suitable crosslinking agents include ethylene glycol dimethacrylate,Ebecyl 150 and the like. Crosslinking agents can be present in thepolymerizable formulation in an amount between about 0.5 wt % and about30.0 wt %. In certain embodiments, crosslinking agents can be present inthe polymerizable formulation in an amount between about 0.5 wt % andabout 3.0 wt %. Crosslinking agents are generally added, for example inan amount of 1% w/w, to improve stability and strength of a polymermatrix which helps avoid cracking of the matrix due to shrinkage uponcuring of the matrix.

Suitable scattering agents include TiO₂, alumina, barium sulfate, PTFE,barium titanate and the like. Scattering agents can be present in thepolymerizable formulation in an amount between about 0.05 wt % and about1.0 wt % Scattering agents are generally added, for example in apreferred amount of about 0.15% w/w, to promote outcoupling of emittedlight.

Suitable rheology modifiers (thixotropes) include fumed silicacommercially available from Cabot Corporation such as TS-720 treatedfumed silica, treated silica commercially available from CabotCorporation such as TS720, TS500, TS530, TS610 and hydrophilic silicasuch as M5 and EHS commercially available from Cabot Corporation.Rheology modifiers can be present in the polymerizable formulation in anamount between about 5% w/w to about 12% w/w. Rheology modifiers orthixotropes act to lower the shrinkage of the matrix resin and helpprevent cracking. Hydrophobic rheology modifiers disperse more easilyand build viscosity at higher loadings allowing for more filler contentand less shrinkage to the point where the formulation becomes tooviscous to fill the tube. Rheology modifiers such as fumed silica alsoprovide higher EQE and help to prevent settling of TiO₂ on the surfaceof the tube before polymerization has taken place.

Suitable fillers include silica, fumed silica, precipitated silica,glass beads, PMMA beads and the like. Fillers can be present in thepolymerizable formulation in an amount between about 0.01% and about60%, about 0.01% and about 50%, about 0.01% and about 40%, about 0.01%and about 30%, about 0.01% and about 20% and any value or range inbetween whether overlapping or not.

Suitable photoinitiators include Irgacure 2022, KTO-46 (Lambert),Esacure 1 (Lambert) and the like. Photoinitiators can be present in thepolymerizable formulation in an amount between about 1% w/w to about 5%w/w. Photoinitiators generally help to sensitize the polymerizablecomposition to UV light for photopolymerization.

In certain embodiments, a polymerizable quantum dot formulation mayfurther include an emission stabilizer, as described in commonly-ownedU.S. Provisional Application No. 61/562,469 filed 22 Nov. 2011.

According to additional aspects, quantum dots are nanometer sizedparticles that can have optical properties arising from quantumconfinement. The particular composition(s), structure, and/or size of aquantum dot can be selected to achieve the desired wavelength of lightto be emitted from the quantum dot upon stimulation with a particularexcitation source. In essence, quantum dots may be tuned to emit lightacross the visible spectrum by changing their size. See C. B. Murray, C.R. Kagan, and M. G. Bawendi, Annual Review of Material Sci., 2000, 30:545-610 hereby incorporated by reference in its entirety.

Quantum dots can have an average particle size in a range from about 1to about 1000 nanometers (nm), and preferably in a range from about 1 toabout 100 nm. In certain embodiments, quantum dots have an averageparticle size in a range from about 1 to about 20 nm (e.g., such asabout 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 nm).In certain embodiments, quantum dots have an average particle size in arange from about 1 to about 10 nm. Quantum dots can have an averagediameter less than about 150 Angstroms (Å). In certain embodiments,quantum dots having an average diameter in a range from about 12 toabout 150 Å can be particularly desirable. However, depending upon thecomposition, structure, and desired emission wavelength of the quantumdot, the average diameter may be outside of these ranges.

Preferably, a quantum dot comprises a semiconductor nanocrystal. Incertain embodiments, a semiconductor nanocrystal has an average particlesize in a range from about 1 to about 20 nm, and preferably from about 1to about 10 nm. However, depending upon the composition, structure, anddesired emission wavelength of the quantum dot, the average diameter maybe outside of these ranges.

A quantum dot can comprise one or more semiconductor materials.

Examples of semiconductor materials that can be included in a quantumdot (including, e.g., semiconductor nanocrystal) include, but are notlimited to, a Group IV element, a Group II-VI compound, a Group II-Vcompound, a Group III-VI compound, a Group III-V compound, a Group IV-VIcompound, a Group compound, a Group II-IV-VI compound, a Group II-IV-Vcompound, an alloy including any of the foregoing, and/or a mixtureincluding any of the foregoing, including ternary and quaternarymixtures or alloys. A non-limiting list of examples include ZnO, ZnS,ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgS, MgSe, GaAs, GaN, GaP, GaSe, GaSb,HgO, HgS, HgSe, HgTe, InAs, InN, InP, InSb, AlAs, AlN, AlP, AlSb, TlN,TlP, TlAs, TlSb, PbO, PbS, PbSe, PbTe, Ge, Si, an alloy including any ofthe foregoing, and/or a mixture including any of the foregoing,including ternary and quaternary mixtures or alloys.

In certain embodiments, quantum dots can comprise a core comprising oneor more semiconductor materials and a shell comprising one or moresemiconductor materials, wherein the shell is disposed over at least aportion, and preferably all, of the outer surface of the core. A quantumdot including a core and shell is also referred to as a “core/shell”structure.

For example, a quantum dot can include a core having the formula MX,where M is cadmium, zinc, magnesium, mercury, aluminum, gallium, indium,thallium, or mixtures thereof, and X is oxygen, sulfur, selenium,tellurium, nitrogen, phosphorus, arsenic, antimony, or mixtures thereof.Examples of materials suitable for use as quantum dot cores include, butare not limited to, ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgS,MgSe, GaAs, GaN, GaP, GaSe, GaSb, HgO, HgS, HgSe, HgTe, InAs, InN, InP,InSb, AlAs, AlN, AlP, AlSb, TlN, TlP, TlAs, TlSb, PbO, PbS, PbSe, PbTe,Ge, Si, an alloy including any of the foregoing, and/or a mixtureincluding any of the foregoing, including ternary and quaternarymixtures or alloys.

A shell can be a semiconductor material having a composition that is thesame as or different from the composition of the core. The shell cancomprise an overcoat including one or more semiconductor materials on asurface of the core. Examples of semiconductor materials that can beincluded in a shell include, but are not limited to, a Group IV element,a Group II-VI compound, a Group II-V compound, a Group III-VI compound,a Group III-V compound, a Group IV-VI compound, a Group I-III-VIcompound, a Group II-IV-VI compound, a Group II-IV-V compound, alloysincluding any of the foregoing, and/or mixtures including any of theforegoing, including ternary and quaternary mixtures or alloys. Examplesinclude, but are not limited to, ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe,CdTe, MgS, MgSe, GaAs, GaN, GaP, GaSe, GaSb, HgO, HgS, HgSe, HgTe, InAs,InN, InP, InSb, AlAs, AlN, AlP, AlSb, TlN, TlP, TlAs, TlSb, PbO, PbS,PbSe, PbTe, Ge, Si, an alloy including any of the foregoing, and/or amixture including any of the foregoing. For example, ZnS, ZnSe or CdSovercoatings can be grown on CdSe or CdTe semiconductor nanocrystals.

In a core/shell quantum dot, the shell or overcoating may comprise oneor more layers. The overcoating can comprise at least one semiconductormaterial which is the same as or different from the composition of thecore. Preferably, the overcoating has a thickness from about one toabout ten monolayers. An overcoating can also have a thickness greaterthan ten monolayers. In certain embodiments, more than one overcoatingcan be included on a core.

In certain embodiments, the surrounding “shell” material can have a bandgap greater than the band gap of the core material. In certain otherembodiments, the surrounding shell material can have a band gap lessthan the band gap of the core material.

In certain embodiments, the shell can be chosen so as to have an atomicspacing close to that of the “core” substrate. In certain otherembodiments, the shell and core materials can have the same crystalstructure.

Examples of quantum dot (e.g., semiconductor nanocrystal) (core)shellmaterials include, without limitation: red (e.g., (CdSe)CdZnS(core)shell), green (e.g., (CdZnSe)CdZnS (core)shell, etc.), and blue(e.g., (CdS)CdZnS (core)shell.)

Quantum dots can have various shapes, including, but not limited to asphere, rod, disk, other shapes, and mixtures of various shapedparticles.

One example of a method of manufacturing a quantum dot (including, forexample, but not limited to, a semiconductor nanocrystal) is a colloidalgrowth process. Colloidal growth occurs by injection of an M donor andan X donor into a hot coordinating solvent. One example of a preferredmethod for preparing monodisperse quantum dots comprises pyrolysis oforganometallic reagents, such as dimethyl cadmium, injected into a hot,coordinating solvent. This permits discrete nucleation and results inthe controlled growth of macroscopic quantities of quantum dots. Theinjection produces a nucleus that can be grown in a controlled manner toform a quantum dot. The reaction mixture can be gently heated to growand anneal the quantum dot. Both the average size and the sizedistribution of the quantum dots in a sample are dependent on the growthtemperature. The growth temperature for maintaining steady growthincreases with increasing average crystal size. Resulting quantum dotsare members of a population of quantum dots. As a result of the discretenucleation and controlled growth, the population of quantum dots thatcan be obtained has a narrow, monodisperse distribution of diameters.The monodisperse distribution of diameters can also be referred to as a“size.” Preferably, a monodisperse population of particles includes apopulation of particles wherein at least about 60% of the particles inthe population fall within a specified particle size range. A populationof monodisperse particles preferably deviate less than 15% rms(root-mean-square) in diameter and more preferably less than 10% rms andmost preferably less than 5%.

An example of an overcoating process is described, for example, in U.S.Pat. No. 6,322,901. By adjusting the temperature of the reaction mixtureduring overcoating and monitoring the absorption spectrum of the core,overcoated materials having high emission quantum efficiencies andnarrow size distributions can be obtained.

The narrow size distribution of the quantum dots (including, e.g.,semiconductor nanocrystals) allows the possibility of light emission innarrow spectral widths. Monodisperse semiconductor nanocrystals havebeen described in detail in Murray et al. (J. Am. Chem. Soc., 115:8706(1993)) and in the thesis of Christopher Murray, entitled “Synthesis andCharacterization of II-VI Quantum Dots and Their Assembly into 3-DQuantum Dot Superlattices”, Massachusetts Institute of Technology,September, 1995. The foregoing are hereby incorporated herein byreference in their entireties.

The process of controlled growth and annealing of the quantum dots inthe coordinating solvent that follows nucleation can also result inuniform surface derivatization and regular core structures. As the sizedistribution sharpens, the temperature can be raised to maintain steadygrowth. By adding more M donor or X donor, the growth period can beshortened. The M donor can be an inorganic compound, an organometalliccompound, or elemental metal. For example, an M donor can comprisecadmium, zinc, magnesium, mercury, aluminum, gallium, indium orthallium, and the X donor can comprise a compound capable of reactingwith the M donor to form a material with the general formula MX. The Xdonor can comprise a chalcogenide donor or a pnictide donor, such as aphosphine chalcogenide, a bis(silyl)chalcogenide, dioxygen, an ammoniumsalt, or a tris(silyl)pnictide. Suitable X donors include, for example,but are not limited to, dioxygen, bis(trimethylsilyl)selenide((TMS)₂Se), trialkyl phosphine selenides such as (tri-noctylphosphine)selenide (TOPSe) or (tri-n-butylphosphine) selenide (TBPSe), trialkylphosphine tellurides such as (tri-n-octylphosphine) telluride (TOPTe) orhexapropylphosphorustriamide telluride (HPPTTe),bis(trimethylsilyl)telluride ((TMS)₂Te), bis(trimethylsilyl)sulfide((TMS)₂S), a trialkyl phosphine sulfide such as (tri-noctylphosphine)sulfide (TOPS), an ammonium salt such as an ammonium halide (e.g.,NH₄Cl), tris(trimethylsilyl)phosphide ((TMS)₃P),tris(trimethylsilyl)arsenide ((TMS)₃As), ortris(trimethylsilyl)antimonide ((TMS)₃Sb). In certain embodiments, the Mdonor and the X donor can be moieties within the same molecule.

A coordinating solvent can help control the growth of the quantum dot. Acoordinating solvent is a compound having a donor lone pair, forexample, a lone electron pair available to coordinate to a surface ofthe growing quantum dot (including, e.g., a semiconductor nanocrystal).Solvent coordination can stabilize the growing quantum dot. Examples ofcoordinating solvents include alkyl phosphines, alkyl phosphine oxides,alkyl phosphonic acids, or alkyl phosphinic acids, however, othercoordinating solvents, such as pyridines, furans, and amines may also besuitable for the quantum dot (e.g., semiconductor nanocrystal)production. Additional examples of suitable coordinating solventsinclude pyridine, tri-n-octyl phosphine (TOP), tri-n-octyl phosphineoxide (TOPO) and trishydroxylpropylphosphine (tHPP), tributylphosphine,tri(dodecyl)phosphine, dibutyl-phosphite, tributyl phosphite,trioctadecyl phosphite, trilauryl phosphite, tris(tridecyl)phosphite,triisodecyl phosphite, bis(2-ethylhexyl)phosphate,tris(tridecyl)phosphate, hexadecylamine, oleylamine, octadecylamine,bis(2-ethylhexyl)amine, octylamine, dioctylamine, trioctylamine,dodecylamine/laurylamine, didodecylamine tridodecylamine,hexadecylamine, dioctadecylamine, trioctadecylamine, phenylphosphonicacid, hexylphosphonic acid, tetradecylphosphonic acid, octylphosphonicacid, octadecylphosphonic acid, propylenediphosphonic acid,phenylphosphonic acid, aminohexylphosphonic acid, dioctyl ether,diphenyl ether, methyl myristate, octyl octanoate, N-dodecylpyrrolidone(NDP) and hexyl octanoate. In certain embodiments, technical grade TOPOcan be used.

In certain embodiments, quantum dots can alternatively be prepared withuse of non-coordinating solvent(s).

Size distribution during the growth stage of the reaction can beestimated by monitoring the absorption or emission line widths of theparticles. Modification of the reaction temperature in response tochanges in the absorption spectrum of the particles allows themaintenance of a sharp particle size distribution during growth.Reactants can be added to the nucleation solution during crystal growthto grow larger crystals. For example, for CdSe and CdTe, by stoppinggrowth at a particular semiconductor nanocrystal average diameter andchoosing the proper composition of the semiconducting material, theemission spectra of the semiconductor nanocrystals can be tunedcontinuously over the wavelength range of 300 nm to 5 microns, or from400 nm to 800 nm.

The particle size distribution of the quantum dots (including, e.g.,semiconductor nanocrystals) can be further refined by size selectiveprecipitation with a poor solvent for the quantum dots, such asmethanol/butanol. For example, quantum dots can be dispersed in asolution of 10% butanol in hexane. Methanol can be added dropwise tothis stirring solution until opalescence persists. Separation ofsupernatant and flocculate by centrifugation produces a precipitateenriched with the largest crystallites in the sample. This procedure canbe repeated until no further sharpening of the optical absorptionspectrum is noted. Size-selective precipitation can be carried out in avariety of solvent/nonsolvent pairs, including pyridine/hexane andchloroform/methanol. The size-selected quantum dot (e.g., semiconductornanocrystal) population preferably has no more than a 15% rms deviationfrom mean diameter, more preferably 10% rms deviation or less, and mostpreferably 5% rms deviation or less.

Semiconductor nanocrystals and other types of quantum dots preferablyhave ligands attached thereto. According to one aspect, quantum dotswithin the scope of the present invention include green CdSe quantumdots having oleic acid ligands and red CdSe quantum dots having oleicacid ligands. Alternatively, or in addition, octadecylphosphonic acid(“ODPA”) ligands may be used instead of oleic acid ligands. The ligandspromote solubility of the quantum dots in the polymerizable compositionwhich allows higher loadings without agglomeration which can lead to redshifting.

Ligands can be derived from a coordinating solvent that may be includedin the reaction mixture during the growth process.

Ligands can be added to the reaction mixture.

Ligands can be derived from a reagent or precursor included in thereaction mixture for synthesizing the quantum dots.

In certain embodiments, quantum dots can include more than one type ofligand attached to an outer surface.

A quantum dot surface that includes ligands derived from the growthprocess or otherwise can be modified by repeated exposure to an excessof a competing ligand group (including, e.g., but not limited to, acoordinating group) to form an overlayer. For example, a dispersion ofthe capped quantum dots can be treated with a coordinating organiccompound, such as pyridine, to produce crystallites which dispersereadily in pyridine, methanol, and aromatics but no longer disperse inaliphatic solvents. Such a surface exchange process can be carried outwith any compound capable of coordinating to or bonding with the outersurface of the nanoparticle, including, for example, but not limited to,phosphines, thiols, amines and phosphates.

For example, a quantum dot can be exposed to short chain polymers whichexhibit an affinity for the surface and which terminate in a moietyhaving an affinity for a suspension or dispersion medium. Such affinityimproves the stability of the suspension and discourages flocculation ofthe quantum dot. Examples of additional ligands include fatty acidligands, long chain fatty acid ligands, alkyl phosphines, alkylphosphine oxides, alkyl phosphonic acids, or alkyl phosphinic acids,pyridines, furans, and amines. More specific examples include, but arenot limited to, pyridine, tri-n-octyl phosphine (TOP), tri-n-octylphosphine oxide (TOPO), tris-hydroxylpropylphosphine (tHPP) andoctadecylphosphonic acid (“ODPA”). Technical grade TOPO can be used.

Suitable coordinating ligands can be purchased commercially or preparedby ordinary synthetic organic techniques, for example, as described inJ. March, Advanced Organic Chemistry, which is incorporated herein byreference in its entirety.

The emission from a quantum dot capable of emitting light can be anarrow Gaussian emission band that can be tuned through the completewavelength range of the ultraviolet, visible, or infra-red regions ofthe spectrum by varying the size of the quantum dot, the composition ofthe quantum dot, or both. For example, a semiconductor nanocrystalcomprising CdSe can be tuned in the visible region; a semiconductornanocrystal comprising InAs can be tuned in the infra-red region. Thenarrow size distribution of a population of quantum dots capable ofemitting light can result in emission of light in a narrow spectralrange. The population can be monodisperse and preferably exhibits lessthan a 15% rms (root-mean-square) deviation in diameter of such quantumdots, more preferably less than 10%, most preferably less than 5%.Spectral emissions in a narrow range of no greater than about 75 nm,preferably no greater than about 60 nm, more preferably no greater thanabout 40 nm, and most preferably no greater than about 30 nm full widthat half max (FWHM) for such quantum dots that emit in the visible can beobserved. IR-emitting quantum dots can have a FWHM of no greater than150 nm, or no greater than 100 nm. Expressed in terms of the energy ofthe emission, the emission can have a FWHM of no greater than 0.05 eV,or no greater than 0.03 eV. The breadth of the emission decreases as thedispersity of the light-emitting quantum dot diameters decreases.

Quantum dots can have emission quantum efficiencies such as greater than10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%.

The narrow FWHM of quantum dots can result in saturated color emission.The broadly tunable, saturated color emission over the entire visiblespectrum of a single material system is unmatched by any class oforganic chromophores (see, for example, Dabbousi et al., J. Phys. Chem.101, 9463 (1997), which is incorporated by reference in its entirety). Amonodisperse population of quantum dots will emit light spanning anarrow range of wavelengths.

Useful quantum dots according to the present invention are those thatemit wavelengths characteristic of red light. In certain preferredembodiments, quantum dots capable of emitting red light emit lighthaving a peak center wavelength in a range from about 615 nm to about635 nm, and any wavelength or range in between whether overlapping ornot. For example, the quantum dots can be capable of emitting red lighthaving a peak center wavelength of about 635 nm, about 630 nm, of about625 nm, of about 620 nm, or of about 615 nm.

Useful quantum dots according to the present invention are also thosethat emit wavelengths characteristic of green light. In certainpreferred embodiments, quantum dots capable of emitting green light emitlight having a peak center wavelength in a range from about 520 nm toabout 545 nm, and any wavelength or range in between whether overlappingor not. For example, the quantum dots can be capable of emitting greenlight having a peak center wavelength of about 520 nm, of about 525 nm,of about 535 nm, of about 540 nm or of about 540 nm.

According to further aspects of the present invention, the quantum dotsexhibit a narrow emission profile in the range of between about 23 nmand about 60 nm at full width half maximum (FWHM). The narrow emissionprofile of quantum dots of the present invention allows the tuning ofthe quantum dots and mixtures of quantum dots to emit saturated colorsthereby increasing color gamut and power efficiency beyond that ofconventional LED lighting displays. According to one aspect, greenquantum dots designed to emit a predominant wavelength of, for example,about 523 nm and having an emission profile with a FWHM of about, forexample, 37 nm are combined, mixed or otherwise used in combination withred quantum dots designed to emit a predominant wavelength of about, forexample, 617 nm and having an emission profile with a FWHM of about, forexample 32 nm. Such combinations can be stimulated by blue light tocreate trichromatic white light.

Quantum dots in accordance with the present invention can be included invarious formulations depending upon the desired utility. According toone aspect, quantum dots are included in flowable formulations orliquids to be included, for example, into clear vessels, such as thestress-resistant tubes of the present invention, which are to be exposedto light. Such formulations can include various amounts of one or moretype of quantum dots and one or more host materials. Such formulationscan further include one or more scatterers. Other optional additives oringredients can also be included in a formulation. In certainembodiments, a formulation can further include one or more photoinitiators. One of skill in the art will readily recognize from thepresent invention that additional ingredients can be included dependingupon the particular intended application for the quantum dots.

An optical material or formulation within the scope of the invention mayinclude a host material, such as can be included in an optical componentdescribed herein, which may be present in an amount from about 50 weightpercent and about 99.5 weight percent, and any weight percent in betweenwhether overlapping or not. In certain embodiments, a host material maybe present in an amount from about 80 to about 99.5 weight percent.Examples of specific useful host materials include, but are not limitedto, polymers, oligomers, monomers, resins, binders, glasses, metaloxides, and other nonpolymeric materials. Preferred host materialsinclude polymeric and non-polymeric materials that are at leastpartially transparent, and preferably fully transparent, to preselectedwavelengths of light. In certain embodiments, the preselectedwavelengths can include wavelengths of light in the visible (e.g.,400-700 nm) region of the electromagnetic spectrum. Preferred hostmaterials include cross-linked polymers and solvent-cast polymers.Examples of other preferred host materials include, but are not limitedto, glass or a transparent resin. In particular, a resin such as anon-curable resin, heat-curable resin, or photocurable resin is suitablyused from the viewpoint of processability. Specific examples of such aresin, in the form of either an oligomer or a polymer, include, but arenot limited to, a melamine resin, a phenol resin, an alkyl resin, anepoxy resin, a polyurethane resin, a maleic resin, a polyamide resin,polymethyl methacrylate, polyacrylate, polycarbonate, polyvinyl alcohol,polyvinylpyrrolidone, hydroxyethylcellulose, carboxymethylcellulose,copolymers containing monomers or oligomers forming these resins, andthe like. Other suitable host materials can be identified by persons ofordinary skill in the relevant art.

Host materials can also comprise silicone materials. Suitable hostmaterials comprising silicone materials can be identified by persons ofordinary skill in the relevant art.

In certain embodiments and aspects of the inventions contemplated bythis invention, a host material comprises a photocurable resin. Aphotocurable resin may be a preferred host material in certainembodiments, e.g., in embodiments in which the composition is to bepatterned. As a photo-curable resin, a photo-polymerizable resin such asan acrylic acid or methacrylic acid based resin containing a reactivevinyl group, a photo-crosslinkable resin which generally contains aphoto-sensitizer, such as polyvinyl cinnamate, benzophenone, or the likemay be used. A heat-curable resin may be used when the photo-sensitizeris not used. These resins may be used individually or in combination oftwo or more.

In certain embodiments and aspects of the inventions contemplated bythis invention, a host material can comprise a solvent-cast resin. Apolymer such as a polyurethane resin, a maleic resin, a polyamide resin,polymethyl methacrylate, polyacrylate, polycarbonate, polyvinyl alcohol,polyvinylpyrrolidone, hydroxyethylcellulose, carboxymethylcellulose,copolymers containing monomers or oligomers forming these resins, andthe like can be dissolved in solvents known to those skilled in the art.Upon evaporation of the solvent, the resin forms a solid host materialfor the semiconductor nanoparticles.

In certain embodiments, acrylate monomers and/or acrylate oligomerswhich are commercially available from Radcure and Sartomer can bepreferred.

Quantum dots can be encapsulated. Nonlimiting examples of encapsulationmaterials, related methods, and other information that may be useful aredescribed in International Application No. PCT/US2009/01372 of Linton,filed 4 Mar. 2009 entitled “Particles Including Nanoparticles, UsesThereof, And Methods” and U.S. Patent Application No. 61/240,932 of Nicket al., filed 9 Sep. 2009 entitled “Particles Including Nanoparticles,Uses Thereof, And Methods”, each of the foregoing being herebyincorporated herein by reference in its entirety.

The total amount of quantum dots included in an optical material, suchas a host material for example a polymer matrix, within the scope of theinvention is preferably in a range from about 0.05 weight percent toabout 5 weight percent, and more preferably in a range from about 0.1weight percent to about 5 weight percent and any value or range inbetween whether overlapping or not. The amount of quantum dots includedin an optical material can vary within such range depending upon theapplication and the form in which the quantum dots are included (e.g.,film, optics (e.g., capillary), encapsulated film, etc.), which can bechosen based on the particular end application. For instance, when anoptic material is used in a thicker capillary with a longer pathlength(e.g., such as in BLUs for large screen television applications), theconcentration of quantum dots can be closer to 0.5%. When an opticalmaterial is used in a thinner capillary with a shorter pathlength (e.g.,such as in BLUs for mobile or hand-held applications), the concentrationof quantum dots can be closer to 5%.

The ratio of quantum dots used in an optical material is determined bythe emission peaks of the quantum dots used. For example, when quantumdots capable of emitting green light having a peak center wavelength ina range from about 514 nm to about 545 nm, and any wavelength in betweenwhether overlapping or not, and quantum dots capable of emitting redlight having a peak center wavelength in a range from about 615 nm toabout 640 nm, and any wavelength in between whether overlapping or not,are used in an optical material, the ratio of the weight percentgreen-emitting quantum dots to the weight percent of red-emittingquantum dots can be in a range from about 12:1 to about 1:1, and anyratio in between whether overlapping or not.

The above ratio of weight percent green-emitting quantum dots to weightpercent red-emitting quantum dots in an optical material canalternatively be presented as a molar ratio. For example, the aboveweight percent ratio of green to red quantum dots can correspond to agreen to red quantum dot molar ratio in a range from about 24.75 to 1 toabout 5.5 to 1, and any ratio in between whether overlapping or not.

The ratio of the blue to green to red light output intensity in whitetrichromatic light emitted by a quantum dot containing BLU describedherein including blue-emitting solid state inorganic semiconductor lightemitting devices (having blue light with a peak center wavelength in arange from about 450 nm to about 460 nm, and any wavelength in betweenwhether overlapping or not), and an optical material including mixturesof green-emitting quantum dots and red-emitting quantum dots within theabove range of weight percent ratios can vary within the range. Forexample, the ratio of blue to green light output intensity therefor canbe in a range from about 0.75 to about 4 and the ratio of green to redlight output intensity therefor can be in a range from about 0.75 toabout 2.0. In certain embodiments, for example, the ratio of blue togreen light output intensity can be in a range from about 1.0 to about2.5 and the ratio of green to red light output intensity can be in arange from about 0.9 to about 1.3.

Scatterers, also referred to as scattering agents, within the scope ofthe invention may be present, for example, in an amount of between about0.01 weight percent and about 1 weight percent. Amounts of scatterersoutside such range may also be useful. Examples of light scatterers(also referred to herein as scatterers or light scattering particles)that can be used in the embodiments and aspects of the inventionsdescribed herein, include, without limitation, metal or metal oxideparticles, air bubbles, and glass and polymeric beads (solid or hollow).Other light scatterers can be readily identified by those of ordinaryskill in the art. In certain embodiments, scatterers have a sphericalshape. Preferred examples of scattering particles include, but are notlimited to, TiO₂, SiO₂, BaTiO₃, BaSO₄, and ZnO. Particles of othermaterials that are non-reactive with the host material and that canincrease the absorption pathlength of the excitation light in the hostmaterial can be used. In certain embodiments, light scatterers may havea high index of refraction (e.g., TiO₂, BaSO₄, etc) or a low index ofrefraction (gas bubbles).

Selection of the size and size distribution of the scatterers is readilydeterminable by those of ordinary skill in the art. The size and sizedistribution can be based upon the refractive index mismatch of thescattering particle and the host material in which the light scatterersare to be dispersed, and the preselected wavelength(s) to be scatteredaccording to light scattering theory, e.g., Rayleigh or Mie scatteringtheory. The surface of the scattering particle may further be treated toimprove dispersability and stability in the host material. In oneembodiment, the scattering particle comprises TiO₂ (R902+ from DuPont)of 0.2 μm particle size, in a concentration in a range from about 0.01to about 1% by weight.

The amount of scatterers in a formulation is useful in applicationswhere the formulation may be in the form of an ink is contained in aclear vessel having edges to limit losses due the total internalreflection. The amount of the scatterers may be altered relative to theamount of quantum dots used in the formulation. For example, when theamount of the scatter is increased, the amount of quantum dots may bedecreased.

Examples of thixotropes which may be included in a quantum dotformulation, also referred to as rheology modifiers, include, but arenot limited to, fumed metal oxides (e.g., fumed silica which can besurface treated or untreated (such as Cab-O-Sil™ fumed silica productsavailable from Cabot Corporation)) or fumed metal oxide gels (e.g., asilica gel). An optical material can include an amount of thixotrope ina range from about 5 to about 12 weight percent. Other amounts outsidethe range may also be determined to be useful or desirable.

In certain embodiments, a formulation including quantum dots and a hostmaterial can be formed from an ink comprising quantum dots and a liquidvehicle, wherein the liquid vehicle comprises a composition includingone or more functional groups or units that are capable of beingcross-linked. The functional units can be cross-linked, for example, byUV treatment, thermal treatment, or another cross-linking techniquereadily ascertainable by a person of ordinary skill in a relevant art.In certain embodiments, the composition including one or more functionalgroups that are capable of being cross-linked can be the liquid vehicleitself. In certain embodiments, it can be a co-solvent. In certainembodiments, it can be a component of a mixture with the liquid vehicle.

One particular example of a preferred method of making an ink is asfollows. A solution including quantum dots having the desired emissioncharacteristics well dispersed in an organic solvent is concentrated tothe consistency of a wax by first stripping off the solvent undernitrogen/vacuum until a quantum dot containing residue with the desiredconsistency is obtained. The desired resin monomer is then added undernitrogen conditions, until the desired monomer to quantum dot ratio isachieved. This mixture is then vortex mixed under oxygen free conditionsuntil the quantum dots are well dispersed. The final components of theresin are then added to the quantum dot dispersion, and are thensonicated mixed to ensure a fine dispersion.

A tube or capillary comprising an optical material prepared from suchfinished ink can be prepared by then introducing the ink into the tubevia a wide variety of methods, and then UV cured under intenseillumination for some number of seconds for a complete cure.

In certain aspects and embodiments of the inventions taught herein, theoptic including the cured quantum dot containing ink is exposed to lightflux for a period of time sufficient to increase the photoluminescentefficiency of the optical material.

In certain embodiments, the optical material is exposed to light andheat for a period of time sufficient to increase the photoluminescentefficiency of the optical material.

In preferred certain embodiments, the exposure to light or light andheat is continued for a period of time until the photoluminescentefficiency reaches a substantially constant value.

In one embodiment, for example, after the optic, i.e. tube or capillary,is filled with quantum dot containing ink, cured, and sealed (regardlessof the order in which the curing and sealing steps are conducted), theoptic is exposed, to 25-35 mW/cm² light flux with a wavelength in arange from about 365 nm to about 470 nm, while at a temperature in arange from about 25 to 80° C., for a period of time sufficient toincrease the photoluminescent efficiency of the ink. In one embodiment,for example, the light has a wavelength of about 450 nm, the light fluxis 30 mW/cm², the temperature 80° C., and the exposure time is 3 hours.

Additional information that may be useful in connection with the presentdisclosure and the inventions described herein is included inInternational Application No. PCT/US2009/002796 of Coe-Sullivan et al,filed 6 May 2009, entitled “Optical Components, Systems Including AnOptical Component, And Devices”; International Application No.PCT/US2009/002789 of Coe-Sullivan et al, filed 6 May 2009, entitled“Solid State Lighting Devices Including Quantum Confined SemiconductorNanoparticles, An Optical Component For A Solid State Light Device, AndMethods”; International Application No. PCT/US2010/32859 of Modi et al,filed 28 Apr. 2010 entitled “Optical Materials, Optical Components, AndMethods”; International Application No. PCT/US2010/032799 of Modi et al,filed 28 Apr. 2010 entitled “Optical Materials, Optical Components,Devices, And Methods”; International Application No. PCT/US2011/047284of Sadasivan et al, filed 10 Aug. 2011 entitled “Quantum Dot BasedLighting”; International Application No. PCT/US2008/007901 of Linton etal, filed 25 Jun. 2008 entitled “Compositions And Methods IncludingDepositing Nanomaterial”; U.S. patent application Ser. No. 12/283,609 ofCoe-Sullivan et al, filed 12 Sep. 2008 entitled “Compositions, OpticalComponent, System Including An Optical Component, Devices, And OtherProducts”; International Application No. PCT/US2008/10651 of Breen etal, filed 12 Sep. 2008 entitled “Functionalized Nanoparticles AndMethod”; U.S. Pat. No. 6,600,175 of Baretz, et al., issued Jul. 29,2003, entitled “Solid State White Light Emitter And Display Using Same”;and U.S. Pat. No. 6,608,332 of Shimizu, et al., issued Aug. 19, 2003,entitled “Light Emitting Device and Display”; each of the foregoingbeing hereby incorporated herein by reference in its entirety.

LEDs within the scope of the present invention include any conventionalLED such as those commercially available from Citizen, Nichia, Osram,Cree, or Lumileds. Useful light emitted from LEDs includes white light,off white light, blue light, green light and any other light emittedfrom an LED.

EXAMPLE I Preparation of Semiconductor Nanocrystals Capable of EmittingRed Light

Synthesis of CdSe Seed Cores:

262.5 mmol of cadmium acetate was dissolved in 3.826 mol oftri-n-octylphosphine at 100° C. in a 3 L 3-neck round-bottom flask andthen dried and degassed for one hour. 4.655 mol of trioctylphosphineoxide and 599.16 mmol of octadecylphosphonic acid were added to a 5 Lstainless steel reactor and dried and degassed at 140° C. for one hour.After degassing, the Cd solution was added to the reactor containing theoxide/acid and the mixture was heated to 310° C. under nitrogen. Oncethe temperature reached 310° C., the heating mantle is removed from thereactor and 731 mL of 1.5 M diisobutylphosphine selenide (DIBP-Se)(900.2 mmol Se) in 1-Dodecyl-2-pyrrolidinone (NDP) was then rapidlyinjected. The reactor is then immediately submerged in partially frozen(via liquid nitrogen) squalane bath rapidly reducing the temperature ofthe reaction to below 100° C. The first absorption peak of thenanocrystals was 480 nm. The CdSe cores were precipitated out of thegrowth solution inside a nitrogen atmosphere glovebox by adding a 3:1mixture of methanol and isopropanol. After removal of themethanol/isopropanol mixture, the isolated cores were then dissolved inhexane and used to make core-shell materials. The isolated materialspecifications were as follows: Optical Density @ 350 nm=2.83; Abs=481nm; Emission=510 nm; FWHM=40 nm; Total Volume=1.9 L of hexane.

Growth of CdSe Cores:

A 1 L glass reactor was charged with 320 mL of 1-octadecene (ODE) anddegassed at 120° C. for 15 minutes under vacuum. The reactor was thenbackfilled with N₂ and the temperature set to 60° C. 120 mL of the CdSeseed core above was injected into the reactor and the hexanes wereremoved under reduced pressure until the vacuum gauge reading was <500mTorr. The temperature of the reaction mixture was then set to 240° C.Meanwhile, two 50 mL syringes were loaded with 80 mL of cadmium oleatein TOP (0.5 M conc.) solution and another two syringes were loaded with80 mL of di-iso-butylphosphine selenide (DiBP-Se) in TOP (0.5 M conc.).Once the reaction mixture reached 240° C., the Cd oleate and DiBP-Sesolutions were infused into the reactor at a rate of 35 mL/hr. The1^(st) excitonic absorption feature of the CdSe cores was monitoredduring infusion and the reaction was stopped at ˜60 minutes when theabsorption feature was 569 nm. The resulting CdSe cores were then readyfor use as is in this growth solution for overcoating.

Synthesis of CdSe/ZnS/CdZnS Core-Shell Nanocrystals:

115 mL of the CdSe core above with a first absorbance peak at 569 nm wasmixed in a 1 L reaction vessel with 1-octadecene (45 mL), and Zn(Oleate) (0.5 M in TOP, 26 mL). The reaction vessel was heated to 120°C. and vacuum was applied for 15 min. The reaction vessel was thenback-filled with nitrogen and heated to 310° C. The temperature wasramped, between 1° C./5 seconds and 1° C./15 seconds. Once the vesselreached 300° C., octanethiol (11.4 mL) was swiftly injected and a timerstarted, Once the timer reached 6 min., one syringe containing zincoleate (0.5 M in TOP, 50 mL) and cadmium oleate (1 M in TOP, 41 mL), andanother syringe containing octanethiol (42.2 mL) were swiftly injected.Once the timer reached 40 min., the heating mantle was dropped and thereaction cooled by subjecting the vessel to a cool air flow. The finalmaterial was precipitated via the addition of butanol and methanol (4:1ratio), centrifuged at 3000 RCF for 5 min, and the pellet redispersedinto hexanes. The sample is then precipitated once more via the additionof butanol and methanol (3:1 ratio), centrifuged, and dispersed intotoluene for storage (616 nm emission, 25 nm FWHM, 80% QY, and 94% EQE infilm).

EXAMPLE II Preparation of Semiconductor Nanocrystals Capable of EmittingGreen Light

Synthesis of CdSe Cores:

262.5 mmol of cadmium acetate was dissolved in 3.826 mol oftri-n-octylphosphine at 100° C. in a 3 L 3-neck round-bottom flask andthen dried and degassed for one hour. 4.655 mol of trioctylphosphineoxide and 599.16 mmol of octadecylphosphonic acid were added to a 5 Lstainless steel reactor and dried and degassed at 140° C. for one hour.After degassing, the Cd solution was added to the reactor containing theoxide/acid and the mixture was heated to 310° C. under nitrogen. Oncethe temperature reached 310° C., the heating mantle was removed from thereactor and 731 mL of 1.5 M diisobutylphosphine selenide (DIBP-Se)(900.2 mmol Se) in 1-Dodecyl-2-pyrrolidinone (NDP) was then rapidlyinjected. The reactor was then immediately submerged in a partiallyfrozen (via liquid nitrogen) squalane bath rapidly reducing thetemperature of the reaction to below 100° C. The first absorption peakof the nanocrystals was 487 nm. The CdSe cores were precipitated out ofthe growth solution inside a nitrogen atmosphere glovebox by adding a3:1 mixture of methanol and isopropanol. The isolated cores were thendissolved in hexane and used to make core-shell materials. The isolatedmaterial specifications were as follows: Optical Density @ 350 nm=1.62;Abs=486 nm; Emission=509 nm; FWHM=38 nm; Total Volume=1.82 L of hexane.

Synthesis of CdSe/ZnS/CdZnS Core-Shell Nanocrystals:

335 mL of 1-octadecene (ODE), 12.55 g of zinc acetate, and 38 mL ofoleic acid were loaded into a 1 L glass reactor and degassed at 100° C.for 1 hour. In a 1 L 3-neck flask, 100 mL of ODE was degassed at 120° C.for 1 hour. After degassing, the temperature of the flask was reduced to65° C. and then 23.08 mmol of CdSe cores from the procedure above (275mL) were blended into the 100 mL of degassed ODE and the hexane wasremoved under reduced pressure. The temperature of the reactor was thenraised to 310° C. In a glove box, the core/ODE solution and 40 mL ofoctanethiol were added to a 180 mL container. In a 600 mL container, 151mL of 0.5 M Zn Oleate in TOP, 37 mL of 1.0 M Cd Oleate in TOP, and 97 mLof 2 M TOP-S were added. Once the temperature of the reactor hit 310°C., the ODE/QD cores/Octanethiol mixture was injected into the reactorand allowed to react for 30 min at 300° C. After this reaction period,the Zn Oleate/Cd Oleate/TOP-S mixture was injected to the reactor andthe reaction was allowed to continue for an additional 30 minutes atwhich point the mixture was cooled to room temperature. The resultingcore-shell material was precipitated out of the growth solution inside anitrogen atmosphere glovebox by adding a 2:1 mixture of butanol andmethanol. The isolated quantum dots (QDs) were then dissolved in tolueneand precipitated a second time using 2:3 butanol:methanol. The QDs werefinally dispersed in toluene. The isolated material specifications wereas follows: Optical Density @ 450 nm (100 Fold Dilution)=0.32; Abs=501nm; Emission=518 nm; FWHM=38 nm; Solution QY=60%; Film EQE=93%.

EXAMPLE III Preparation of Polymerizable Formulation Including QuantumDots

A polymerizable formulation including quantum dots was prepared asfollows:

-   -   A clean, dry Schlenk flask equipped with a magnetic stir bar and        rubber septum was charged with 57.75 mL lauryl methacrylate        (LMA) (Aldrich Chemical, 96%), 9.93 mL ethylene glycol        diacrylate (EGDMA) as well as any additive(s) indicated for the        particular example The solution was inerted using a vacuum        manifold and degassed in a standard protocol by        freeze-pump-thawing the mixture three times successively using        liquid nitrogen. The thawed solution is finally placed under        nitrogen and labeled “monomer solution”.    -   Separately, a clean, dry Schlenk flask equipped with a magnetic        stir bar and rubber septum was charged with 6.884 g treated        fumed silica (TS-720, Cabot Corp), 103.1 mg titanium dioxide        (R902+, DuPont Corp.) and inerted under nitrogen. To this is        added 69 mL toluene (dry and oxygen free). The mixture is placed        in an ultrasonic bath for 10 minutes and then stirred under        nitrogen. This is labeled “metal oxide slurry”.    -   Separately, a clean, dry Schlenk flask equipped with a magnetic        stir bar and rubber septum was inerted under nitrogen. The flask        was then charged with a green quantum dot solution (13.1 mL of        quantum dots prepared as generally described in Example II        above) in toluene, red quantum dot solution (2.55 mL of quantum        dots prepared as generally described in Example I above) in        toluene and 69 mL additional toluene via syringe and allowed to        stir for 5 minutes. Over 6 minutes, the contents of the “monomer        solution flask” were added via syringe and stirred for an        additional five minutes. The contents of the “metal oxide        slurry” flask were next added over 5 minutes via cannula and        rinsed over with the aid of a minimum amount of additional        toluene.

The stirred flask was then placed in a warm water bath (<60° C.),covered with aluminum foil to protect from light and placed under avacuum to remove all of the toluene to a system pressure of <200 mtorr.After solvent removal was completed, slurry was removed from heat and,with stirring, 640 μL Irgacure 2022 photoinitiator (BASF), withoutpurification, was added via syringe and allowed to stir for 5 minutes.The final ink was then ready for transfer to a fill station.

EXAMPLE IV Filling Capillary, Forming Quantum Dot Matrix, and CapillarySealing

A stress-resistant tube was filled under oxygen free conditions with thequantum dot formulation of Example III as follows. Glass capillaries aremaintained in a vacuum drying oven under nitrogen for 12 hours at apressure of less than 1 torr and a temperature of 120° C. A quantum dotink formulation of Example III is maintained in a quantum dot ink vesselunder nitrogen. Capillaries with both ends open are removed from thevacuum drying oven and placed into a vacuum fill vessel with an open enddown into quantum dot ink. The quantum dot ink vessel is connected tothe vacuum fill vessel via tubing and valves such that ink is able toflow from the quantum dot ink vessel to the vacuum fill vessel byapplying pressure differentials. The pressure within the vacuum fillvessel is reduced to less than 200 torr and then repressurized withnitrogen. Quantum dot ink is admitted into the vacuum fill vessel bypressurization of the quantum dot ink vessel and the capillaries wereallowed to fill under oxygen free conditions. Alternatively, the vacuumfill vessel can be evacuated thereby drawing the fluid up into thecapillaries. After the capillaries are filled, the system is bled toatmospheric pressure. The exterior of the capillaries is then cleanedusing toluene.

According to an additional embodiment with reference to FIG. 2, acapillary with one end sealed is connected to a filling head. Thecapillary is evacuated by vacuum. Quantum dot ink under nitrogenpressure is then filled into the capillary. The lines and filling headis flushed with nitrogen. The capillary is then removed from the fillinghead under an atmosphere of nitrogen or nitrogen is backfilled into thecapillary and the end sealed, such as by melting the capillary end andsealing.

The polymerizable formulation within the glass tube is polymerized asfollows. The tubes are transferred to a photopolymerization reactorwhere the tubes are placed on a continuously moving belt and exposed for30 seconds to light from a mercury “H” or “D” lamp at a fluence of250-1000 J/cm. After polymerization, the tubes are end sealed,preferably under a nitrogen atmosphere, using an epoxy. Alternatively,with reference to FIG. 2, the quantum dot ink in the sealed capillary isthen cured within the capillary through exposure to ultra violet lightof 395 nm wavelength or equivalent wavelength.

The completed, sealed capillary(ies) were exposed to 30 mW/cm² lightflux with a wavelength of about 450 nm, for 12 hours at 60° C. prior toany analytical testing.

EXAMPLE V

Crack Resistance of Tube of Invention Compared to Prior Art Tube

The improved stress resistance of the tubes of the present invention wasdetermined by comparing the frequency of cracking of thestress-resistant tube to prior art tubes having a square configurationusing the same polymerizable formulation and the same polymerization andcuring conditions. The results show little to no cracking of thestress-resistant tubes with significant cracking of the prior art tubes.Prior art tubes that have a rectangular type cross section show a highfrequency of cracking along the edge, especially after the quantum dotink has been cured within. FIG. 3 shows a photomicrograph of the type ofcrack that can be eliminated with use of the tube design of the presentinvention. The prior art capillary was filled with quantum dot ink andcured as described in Example IV. Edge cracks developed immediatelyalong the edges of the tube as shown in the figure.

EXAMPLE VI Light Emission Characteristics

The polymerized formulation within the stress-resistant tube wassubjected to blue light from an LED.

A failure of the integrity of the capillary can adversely affect thestability of quantum dot ink. The integrity of the capillary with aquantum dot ink is tested on a setup. The setup consists of an array ofblue LED with peak wavelength of 445 nm. A test capillary is subjectedto a blue light flux of ˜400 mW blue optical power/LED. The testcapillary is held at a distance of about 0.6 mm above the LED array.

The emission spectra of the test capillary with red and green quantumdots were captured prior to the start of the blue light exposure. Thisis done by exciting the red and green quantum dots with a 445 nm bluelight source and measuring the resultant spectra in an half moonintegrating sphere. The test (capillary without cracks) and control(capillary with cracks) were tested prior to aging. The sample was thenaged in the above mentioned setup for 87 hrs. The quantum dots in thecracked capillary (control) started to show degradation while thequantum dots in the capillary without cracks (test) showed no signs ofdegradation.

FIG. 4 shows the normalized spectra of the quantum dot ink in thecontrol (capillary with cracks) capillary measured at time t=0 and t=87hrs. The red and green peaks located at 627 nm and 533 nm respectivelyshow loss in intensity. This loss in intensity is due to the degradationof red and green quantum dots in the cracked capillary

FIG. 5 shows the normalized spectra of the quantum dot ink in the test(capillary without cracks) capillary measured at time t=0 and t=87 hrs.The red and green peaks located at 627 nm and 533 nm respectively showno change in intensity. Quantum dots in the capillary without cracksshow no degradation.

“Solid state external quantum efficiency” (also referred to herein as“EQE” or “solid state photoluminescent efficiency) can be measured in a12” integrating sphere using a NIST traceable calibrated light source,using the method developed by Mello et al., Advanced Materials 9(3):230(1997), which is hereby incorporated by reference. Such measurements canalso be made with a QEMS from LabSphere (which utilizes a 4 in sphere;e.g. QEMS-2000: World Wide Websitelaser2000.nl/upload/documenten/fop_21-en2.pdf).

As used herein, the singular forms “a”, “an” and “the” include pluralunless the context clearly dictates otherwise. Thus, for example,reference to an emissive material includes reference to one or more ofsuch materials.

Applicants specifically incorporate the entire contents of all citedreferences in this disclosure. Further, when an amount, concentration,or other value or parameter is given as either a range, preferred range,or a list of upper preferable values and lower preferable values, thisis to be understood as specifically disclosing all ranges formed fromany pair of any upper range limit or preferred value and any lower rangelimit or preferred value, regardless of whether ranges are separatelydisclosed. Where a range of numerical values is recited herein, unlessotherwise stated, the range is intended to include the endpointsthereof, and all integers and fractions within the range. It is notintended that the scope of the invention be limited to the specificvalues recited when defining a range.

Other embodiments of the present invention will be apparent to thoseskilled in the art from consideration of the present specification andpractice of the present invention disclosed herein. It is intended thatthe present specification and examples be considered as exemplary onlywith a true scope and spirit of the invention being indicated by thefollowing claims and equivalents thereof.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

What is claimed is:
 1. A glass tube for use with quantum dotformulations comprising the glass tube defined by a light transmissivewall, the glass tube having a length dimension and a cross-sectionperpendicular to the length dimension, the cross-section including afirst full semicircle end and an opposite second full semicircle end anda pair of substantially parallel walls connecting the first fullsemicircle end and the second full semicircle end with the substantiallyparallel walls defining a uniform path length, wherein the glass tubehas an internal cross-sectional area to glass cross-sectional area ratioless than 0.7, wherein the full semicircle ends have an averagethickness along the length of the tube which is smaller than the averagethickness of the straight substantially parallel walls along the lengthof the tube.
 2. An optical component comprising a glass tube defined bya light transmissive wall, the glass tube having a length dimension anda cross-section perpendicular to the length dimension, the cross-sectionincluding a first full semicircle end and an opposite second fullsemicircle end and a pair of straight substantially parallel wallsconnecting the first full semicircle end and the second full semicircleend with the substantially parallel walls defining a uniform pathlength, wherein the glass tube has an internal cross-sectional area toglass cross-sectional area ratio less than 0.7, wherein the fullsemicircle ends have an average thickness along the length of the tubewhich is smaller than the average thickness of the straightsubstantially parallel walls along the length of the tube; and a matrixincluding quantum dots contained within the glass tube.
 3. A combinationcomprising a glass tube defined by a light transmissive wall, the glasstube having a length dimension and a cross-section perpendicular to thelength dimension, the cross-section including a first full semicircleend and an opposite second full semicircle end and a pair ofsubstantially parallel walls connecting the first full semicircle endand the second full semicircle end with the substantially parallel wallsdefining a uniform path length, wherein the glass tube has an internalcross-sectional area to glass cross-sectional area ratio less than 0.7,wherein the full semicircle ends have an average thickness along thelength of the tube which is smaller than the average thickness of thestraight substantially parallel walls along the length of the tube; amatrix including quantum dots contained within the glass tube; one ormore light sources adjacent to the glass tube; and a light guideadjacent to the glass tube.
 4. A back light display unit comprising oneor more light sources; a glass tube adjacent the one or more lightsources with the glass tube defined by a light transmissive wall, theglass tube having a length dimension and a cross-section perpendicularto the length dimension, the cross-section including a first fullsemicircle end and an opposite second full semicircle end and a pair ofsubstantially parallel walls connecting the first full semicircle endand the second full semicircle end with the substantially parallel wallsdefining a uniform path length, wherein the glass tube has an internalcross-sectional area to glass cross-sectional area ratio less than 0.7,wherein the full semicircle ends have an average thickness along thelength of the tube which is smaller than the average thickness of thestraight substantially parallel walls along the length of the tube; amatrix including quantum dots contained within the glass tube; and alight guide interconnecting a substantially parallel wall of the glasstube and a display unit.
 5. An optical component in accordance withclaim 2 wherein the glass tube containing the matrix is hermeticallysealed with a glass seal.
 6. An optical component in accordance withclaim 2 wherein the glass tube has a racetrack shaped cross-sectionalconfiguration wherein the glass tube is stress-tolerant to stresses onthe tube due to polymerization and curing of a polymerizable quantum dotformulation within the tube.